Until now, there has only been one common method practiced for recovering energy from the treatment of organics associated with a waste stream. This commonly practiced method utilizes the anaerobic conversion process commonly known throughout the industry as a “primary” biological treatment process. This process recovers the methane gas generated from the decomposition of organic matter that takes place within the anaerobic reactor and uses it for fuel to power a motor that in turn runs a generator to generate electricity.
There are many drawbacks and disadvantages to the above noted method and the present invention addresses and resolves these drawbacks and disadvantages in a manner heretofore not taught. Some of the disadvantages of the anaerobic reactor biogas generation process is it is very operator intensive, it is extremely odorous, the process is very volatile and non forgiving as it is a direct result of deriving a benefit from the biological process which has many fluctuating factors which aren't consistent and there fore must be monitored very closely by trained and qualified operating engineers. The process is explosive thereby representing a danger. It is very corrosive which causes high maintenance requirements and associated costs. And the recovery benefit is generally less than a third of the required energy to operate the process.
Another recent approach is the development of the microbial fuel cell. However, this is also a method of utilizing anaerobic digestion. In this hybrid of the anaerobic reactor process, wastewater is treated anaerobically using a bacterial biofilm growing on one electrode of the fuel cell. As can be seen, the microbial fuel cell may have promise, but for now is just a hybrid of the conventional anaerobic biogas generator sharing many of the disadvantages of the same.
As of now, large amounts of energy in the form of electricity are being used in the name of sanitation and protection of the public health and the environment. However, until now, there have not been methods or processes that efficiently recover that electricity used in a conventional secondary treatment process. This is a substantial amount of non-recovered energy consumed per day.
In 2001, PG&E conducted a study on twelve (12) treatment processes. The plant flow ranged from 1.7 MGD to 60.4 MGD. The electricity use ranged from 978 kWh/MG/day to 4,630 kWh/MG/day. The energy used for aeration represented 27% to 82% of the total plant operation electricity requirement.
In 1999, a Multi-Agency Study was conducted by seven (7) participating agencies. That study found that treatment costs of facilities studied ranged from $530/MG/day to $976/MG/day, averaging out at $729/MG/day. The objective of this present invention is to recover as much electricity as possible to offset the cost of providing the treatment.
As the turbulence within the aeration basins are a result of a necessity to provide aeration and mixing in every waste treatment plant that exists, we must capitalize on this requirement and establish the way to have the renewable resource as a result.